KVM: x86: Call-far should not be emulated as stack op

Far call in 64-bit has a 32-bit operand size. Remove the marking of this
operation as Stack so it can be emulated correctly in 64-bit.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>